1. Field of the Invention
The present invention relates to a method of manufacturing a laser light source as a light source of optical application products such as light communication, optical fiber amplifiers, and the like.
2. Description of the Related Art
Conventionally, there has known a laser light source manufacturing method disclosed in Electron. Lett., Vol. 27, No. 13, pp. 1,115 to 1,116, 1991, D. M. Bird et al. According to this method, standard single-mode optical fibers are connected to opposite ends of an optical fiber type diffraction grating respectively, and the end surface of one of the optical fibers is lens-finished.
There is another example of the laser light source manufacturing method disclosed in the international publication WO94/17488 by Raman KASHYAP. This technique comprises a first step of preparing a semiconductor laser having an output facet and a back facet disposed at its opposite ends to constitute an oscillator; a second step of lens-finishing the forward end of an optical fiber; a third step of coupling light emitted from the semiconductor laser with the optical fiber; and a fourth step of radiating interference light of ultraviolet rays through a window opened in a package storing the semiconductor laser and the optical fiber to thereby form a diffraction grating area having a plurality of refractive index changing portions in the core of the optical fiber along the direction of its optical axis.
In the conventional method by D. M. Bird et al. described above, there is a problem that the optical fiber having a diffraction grating has a mechanical connection point, so that it is low in strength as well as in reliability.
In the example of the method disclosed in the above international publication WO94/17488 by Raman KASHYAP, the optical fiber type diffraction grating area is formed after the optical fiber is fixed to the semiconductor laser mechanically so that faults arising in manufacturing the optical fiber type diffraction grating can produce corresponding faults in the laser light source as a whole.
Generally, the cost associated with producing a device constituting a laser light source (hereinafter referred to as xe2x80x9claser oscillating devicexe2x80x9d) other than an optical fiber type diffraction grating is considerably higher than the cost associated with producing the optical fiber type diffraction grating.
However a high-level technique is required for manufacturing an optical fiber type diffraction grating capable of at a reflecting light of desired Bragg wavelength, and the success rate thereof is generally considerably lower than that of manufacturing a laser oscillating device.
It is an object of the present invention to provide a method of manufacturing a laser light source having a high reliability with a high success rate.
In a method of manufacturing a laser light source according to the present invention, an optical fiber having a diffraction grating is produced in which a plurality of refractive index changing portions are formed along the direction of an optical axis of the optical fiber. The optical fiber having the diffraction grating is inserted into a ferrule, the optical fiber is bonded to the ferrule , and the end surface of the ferrule is ground. A laser oscillating device is prepared, and the laser oscillating device is coupled with the optical fiber having the diffraction grating and being inserted in the ferrule.
The present invention provides a laser light source and a manufacturing method thereof with a high success rate by adopting a method where an optical fiber type diffraction grating (which typically has the lowest success rate of manufacturing when manufactured with other components of a laser light source), is manufactured separately from the laser oscillating device so that only one product is connected to the laser oscillating device.
In addition, the present invention provides a laser light source and a manufacturing method thereof with a high reliability by adopting a structure where a portion having the diffraction grating of the optical fiber is received in a ferrule so as to reinforce the optical fiber type diffraction grating and to make the handling thereof easy. As a result, it is easy to provide a minute inclination relative to the optical fiber end surface. Accordingly, it is possible to eliminate reflected light on the end surface of the optical fiber to thereby reduce noise.